February 1997 arXiv papers — page 4

Rong-Gen Cai, Y. S. Myung

We study the critical behavior in the black p-branes and four dimensional charged dilaton black holes. We calculate the thermodynamic fluctuations in the various (microcanonical, canonical, and grandcanonical) ensembles. It is found that the extremal limit of some black configurations has a critical point and a phase transition takes place from the extremal

Q. Y. Liu, S. T. Petcov

Assuming three flavour neutrino mixing takes place in vacuum, we investigate the possibility that the solar nu_e take part in MSW transitions in the Sun due to Delta m^2_{31} from 10^{-7} eV^2 to 10^{-4} eV^2, followed by long wave length vacuum oscillations on the way to the Earth, triggered by Delta m^2_{21} (or Delta m^2_{32}) from 10^{-12} eV^2 to 10^{-1

Frank Ferrari

At an elementary level, we present some non-perturbative aspects of non-abelian gauge theories in four dimensional space-time. Some rigorous results have been obtained in the framework of supersymmetric theories, and a very rich physics related to the strong-coupling dynamics of gauge fields has been discovered. Some of the new phenomena which appeared may p

J. Dias de Deus, C. Pajares, C. A. Salgado

Cumulant oscillations, or $H_q$ moment oscillations, appear if the KNO multiparticle distribution decreases at large z, $z\equiv n/ <n>$, faster than the exponential, $exp(-D z^μ)$, with $μ> 1$. In nucleus-nucleus interactions this behaviour is related to the limitation in the average number of elementary central collisions (or average number of strings cent

J. Dias de Deus, C. Pajares, C. A. Salgado

We show that in high energy nucleus-nucleus collisions the transverse energy or multiplicity distribution P_C, associated to the production of a rare, unabsorbed event C, is universally related to the standard or minimum bias distribution P by the equation $P_C(ν)={ν\over<ν>}P(ν)$, with $\sum P(ν)=1$ and $ν\equiv E_T$ or n. Deviations from this formula are d

V. B. Svetovoy

Zero modes of strings in the abelian Higgs model are analyzed. In spite of the fact that the gauge symmetry is not broken in the string center, the corresponding zero mode is shown to exist and to see it one has to analyze carefully the dependence on transverse coordinates for the excitations. The analysis of this kind is also important for the Witten model

Harold W. Fearing, Randy Lewis, Nader Mobed, Stefan Scherer

The matrix element for muon capture by a proton is calculated to O(p^3) within heavy baryon chiral perturbation theory using the new O(p^3) Lagrangian of Ecker and Mojzis. External nucleon fields are renormalized using the appropriate definition of the wave function renormalization factor Z_N. Our expression for Z_N differs somewhat from that found in existi

J. Kalinowski, P. M. Zerwas

The region of the supersymmetry parameter space, in which charginos decay predominantly into sneutrinos and leptons: chi+ -> \tildeν + l+, is not excluded experimentally for small mass differences between charginos and sneutrinos. The decay sneutrinos are invisible in R-parity conserving theories since they are either the lightest supersymmetric particles or

S. Abachi

We have measured the ZZ-gamma and Z-gamma-gamma couplings by studying p-bar p -> (missing ET) gamma + X events at sqrt(s)=1.8 TeV with the D0 detector at the Fermilab Tevatron Collider. This first study of hadronic Z-gamma production in the neutrino decay channel gives the most stringent limits on anomalous couplings available. A fit to the transverse energy

Andrzej J. Maciejewski, Marek Szydlowski

In this work, we are investigating the problem of integrability of Bianchi class A cosmological models. This class of systems is reduced to the form of Hamiltonian systems with exponential potential forms. The dynamics of Bianchi class A models is investigated through the Euler-Lagrange equations and geodesic equations in the Jacobi metric. On this basis, we

R. Cote, A. H. MacDonald, Luis Brey, H. A. Fertig

At Landau level filling factors near nu =1, quantum Hall ferromagnets form a Skyrme crystal state with quasi-long-range translational and non-collinear magnetic order. We develop an effective low energy theory which explains the presence in these systems of magnetic excitations at low energies below the Larmor gap (Delta) and which predicts a dramatic enhanc

O. Tchernyshyov, Y. J. Uemura

We discuss the normal state of a fermionic system in an idealized PSEUDOGAP REGIME, $k_B T_c < k_B T << |Δ| << E_F$. Stable Cooper pairs induce a pseudogap of width $|Δ|$ in the fermion energy spectrum. Near two dimensions, we find a Bose-like condensation temperature in this predominantly fermionic system.

J. M. G. Vilar, J. M. Rubí

We show the appearance of spatiotemporal stochastic resonance in the Swift-Hohenberg equation. This phenomenon emerges when a control parameter varies periodically in time around the bifurcation point. By using general scaling arguments and by taking into account the common features occurring in a bifurcation, we outline possible manifestations of the phenom

M. V. Entin, G. M. Entin

The properties of the similarity transformation in percolation theory in the complex plane of the percolation probability are studied. It is shown that the percolation problem on a two-dimensional square lattice reduces to the Mandelbrot transformation, leading to a fractal behavior of the percolation probability in the complex plane. The hierarchical chains

S. Hanany, MAXIMA Collaboration, BOOMERANG Collaboration

MAXIMA and BOOMERanG are balloon borne experiments designed to map the cosmic microwave background anisotropy power spectrum from l=10 to l=900 with high resolution. Here we describe the program of observations, the experiments, their capabilities, and their expected performance.

C. Alcock, W. H. Allen, R. A. Allsman, D. Alves

We present analysis of MACHO Alert 95-30, a dramatic gravitational microlensing event towards the Galactic bulge whose peak magnification departs significantly from the standard point-source microlensing model. Alert 95-30 was observed in real-time by the Global Microlensing Alert Network (GMAN), which obtained densely sampled photometric and spectroscopic d

K. Weis, W. J. Duschl, D. J. Bomans, Y. -H. Chu

HR Carinae is one of the few Luminous Blue Variables (LBVs) in the Galaxy. It has a nebula that appears bipolar. We have obtained imaging and high-dispersion, long-slit echelle data of the HR Car nebula, and confirmed that it is a bipolar nebula. Its polar axis lies along the position angle of 125 +- 5 degree; each lobe has, at a distance of 5 kpc a diameter

Apostolos Pilaftsis

We analyze CP violation in resonant transitions involving scalar as well as fermionic intermediate states, using a gauge-invariant resummation approach implemented by the pinch technique. We derive the necessary conditions for resonantly enhanced CP violation induced by particle mixing, by paying special attention to CPT invariance, and apply the results of

Debajyoti Choudhury, Sreerup Raychaudhuri

We examine the possibility that the high-Q^2 events seen at HERA are due to the production and decay of squarks of R-parity violating supersymmetry. The relevant R-parity violating coupling(s) is identified and shown to lie between 0.03 and 0.26. Consequences of such a coupling at other experiments, such as the LEP and Tevatron, are discussed.

P. R. I. Tommasini, P. L. Natti, E. R. Takano Natti, A. F. R. de Toledo Piza

We investigate ground-state and excitation spectrum of a system of non-relativistic bosons in one-dimension interacting through repulsive, two-body contact interactions in a self-consistent Gaussian mean-field approximation. The method consists in writing the variationally determined density operator as the most general Gaussian functional of the quantized f

C. Ciliberto, R. Miranda

Fixing $n$ general points $p_i$ in the plane, what is the dimension of the space of plane curves of degree $d$ having multiplicity $m_i$ at $p_i$ for each $i$? In this article we propose an approach to attack this problem, and demonstrate it by successfully computing this dimension for all $n$ and for $m_i$ constant, at most 3. This application, while previo

Joan Sola

I present an updated discussion of the one-loop corrections to the standard top quark decay, t-> W^+ b, and to the charged Higgs mode, t-> H^+ b, within the framework of the MSSM. These higher order contributions to the top width are compared with the direct top decays into 2 and 3 real SUSY particles. It turns out that whereas the SUSY effects on t-> W^+ b

J. Lehar, B. F. Burke, S. R. Conner, E. E. Falco

We report the discovery of a new gravitationally lensed radio source. Radio maps of MG0751+2716 show four lensed images, which, at higher resolution, are resolved into long arcs of emission. A group of galaxies is present in optical images, including the principal lensing galaxy, with a much brighter galaxy just a few arcseconds away. We have measured the re

V. L. Eletsky, B. L. Ioffe

The mass shift $Δm_N$ of a nucleon in the finite temperature pion gas is calculated in the case of an arbitrary nucleon momentum. A general formula is used which relates the in-medium mass shift $Δm(E)$ of a particle to the real part of the forward scattering amplitude $Re f(E)$ of this particle on constituents of the medium and its applicability domain is f

David Brown

Pair creation of electrically charged black holes and its dual process, pair creation of magnetically charged black holes, are considered. It is shown that the creation rates are equal provided the boundary conditions for the two processes are dual to one another. This conclusion follows from a careful analysis of boundary terms and boundary conditions for t

Peter Varga

We construct integrable modifications of 2d lattice gauge theories with finite gauge groups.

J. L. Goity, Longzhe Zhang

The decays $K_L \to γγ$ and $K_L \to \ell^+ \ell^- γ$ are studied at the leading order $p^6$ in Chiral Perturbation Theory. One-loop contributions stemming from the odd intrinsic parity $|ΔS| = 1$ effective Lagrangian of order $p^4$ are included and shown to be of possible relevance. They affect the decay $K_L \to γγ$ adding to the usual pole terms a piece f

Brian P. Dolan

A metric is introduced on the space of parameters (couplings) describing the large N limit of the O(N) model in Euclidean space. The geometry associated with this metric is analysed in the particular case of the infinite volume limit in 3 dimensions and it is shown that the Ricci curvature diverges at the ultra-violet (Gaussian) fixed point but is finite and

G. Cvetic

Top quark condensation, in particular the minimal framework where the neutral Higgs scalar is (predominantly) an effective ${\bar t} t$ condensate of the Standard Model, is reviewed. Computational approaches are compared and similarities, differences and deficiencies pointed out. Extensions of the minimal framework, including scenarios with two composite Hig

Arlin Crotts, Yihu Fang

Probing the size and shape of the absorbers that lie in front of the QSOs, in particular the Ly alpha forest, we analyze 785 absorption lines in spectra of five QSOs in close groupings: a pair and a triplet. Both QSO groups have been observed before, but these data are a drastic improvement over earlier data, and provide a qualitatively different view of the

Arlin Crotts, Scott Burles, David Tytler

We observe with Keck/HIRES the z ~ 2.5 QSO triplet 1623+27 in order to explore on the scale of a Megaparsec the spatial clustering of C IV absorbers between adjacent sightlines. We find this signal to be significantly weaker than the clustering in velocity on corresponding scales along single sightlines, assuming that the relative velocity of absorbers is do

A. K. Grant, A. G. Morgan, S. Nussinov, R. D. Peccei

We present an estimate of certain higher order corrections to the contribution of the charm triangle loop in the inclusive B -> X_s gamma decay rate, recently discussed by Voloshin. We find that these corrections are minute and hence the result found by Voloshin, although small, is quite robust.

Xiangdong Ji, W. Melnitchouk, X. Song

An extensive theoretical analysis of off-forward parton distributions (OFPDs) is presented. The OFPDs and the form factors of the quark energy-momentum tensor are estimated at a low-energy scale using a bag model. Relations among the second moments of OFPDs, the form factors, and the fraction of the nucleon spin carried by quarks are discussed.

Matt Visser

In this note I introduce the notion of the ``reliability horizon'' for semi-classical quantum gravity. This reliability horizon is an attempt to quantify the extent to which we should trust semi-classical quantum gravity, and to get a better handle on just where the Planck regime resides. I point out that the key obstruction to pushing semi-classical quantum

P. Rozmej, R. Arvieu, W. Berej

The article discusses the properties of time evolution of wave packets in a few systems. Dynamics of wave packet motion for Rydberg atoms with the hierarchy of collapses and revivals is briefly reviewed. The main part of the paper focuses on the new mechanism of quantum reccurrences in wave packet dynamics. This mechanism can occur (in principle) in any phys

R. Arvieu, P. Rozmej, W. Berej

We have found a new class of time dependent partial waves which are solutions of time dependent Schrödinger equation for three dimensional harmonic oscillator. We also showed the decomposition of coherent states of harmonic oscillator into these partial waves. This decomposition appears perticularly convenient for a description of the dynamics of a wave pack

C. Dong, H. Li, G. Mason

Let V be a vertex operator algebra and g an automorphism of order T. We construct a sequence of associative algebras A_{g,n}(V) with n\in\frac{1}{T}\Z nonnegative such that A_{g,n}(V) is a quotient of A_{g,n+1/T}(V) and a pair of functors between the category of A_{g,n}(V)-modules which are not A_{g,n-1/T}(V)-modules and the category of admissible V-modules.

J. A. de Azcárraga, P. P. Kulish, F. Rodenas

We analyze the h-deformations of the Lorentz group and their associated spacetimes. We prove that they have a twisted character and give explicitly the twisting matrices. After studying the representations of one of the deformed spacetime algebras, we discuss the Klein-Gordon operator. It is found that the h-deformed d&#39;Alembertian has plane wave solution

V. S. Varadarajan

The theme of doing quantum mechanics on all abelian groups goes back to Schwinger and Weyl. If the group is a vector space of finite dimension over a non-archimedean locally compact division ring, it is of interest to examine the structure of dynamical systems defined by Hamiltonians analogous to those encountered over the field of real numbers. In this lett

David Hestenes, Jane Jackson

To meet National Standards recommended by the National Research Council for high school physics, inservice teachers must be integrated into the physics community. They must be empowered by access to resources of the physics community and by sustained support for their professional development. To that end, university and college physics departments must assu

Ute Ebert, Wim van Saarloos, Christiane Caroli

Streamers often constitute the first stage of dielectric breakdown in strong electric fields: a nonlinear ionization wave transforms a non-ionized medium into a weakly ionized nonequilibrium plasma. New understanding of this old phenomenon can be gained through modern concepts of (interfacial) pattern formation. As a first step towards an effective interface

Ute Ebert, Wim van Saarloos, Christiane Caroli

Streamers often constitute the first stage of dielectric breakdown in strong electric fields: a nonlinear ionization wave transforms a non-ionized medium into a weakly ionized nonequilibrium plasma. New understanding of this old phenomenon can be gained through modern concepts of (interfacial) pattern formation. As a first step towards an effective interface

Kapil M. S. Bajaj, David S. Cannell, Guenter Ahlers

We present experimental results for pattern formation in Rayleigh-Benard convection of a fluid with a Prandtl number, Pr~ 4. We find that the spiral-defect-chaos (SDC) attractor which exists for Pr~1 has become unstable. Gradually increasing the temperature difference from below to well above its critical value no longer leads to SDC. A sudden jump of temper

David G. Madland

Contains the conclusions and recommendations from this meeting regarding future experimental and theoretical work on the medium-energy nucleon-nucleus optical model.

O. Civitarese, M. Reboiro, P. Vogel

We investigate the BCS treatment of neutron-proton pairing involving time-reversed orbits. We conclude that an isospin-symmetric hamiltonian, treated with the help of the generalized Bogolyubov transformation, fails to describe the ground state pairing properties correctly. In order for the np isovector pairs to coexist with the like-particle pairs, one has

U. Mosel

The observable consequences of a lowering of the restmasses of vector mesons on dilepton spectra in the SIS energy regime (HADES) and on photoabsorption cross sections on nuclei are studied in a transporttheoretical framework. We also investigate the consequences of a mass-shift of kaons in dense matter and compare with recent SIS data. The need for a detail

Andrei Gabrielov

Let P(x) be a germ at the origin of an analytic function in C^n, where x = (x_1,..., x_n), and let ξ= ξ_1(x) d/dx_1 + ... + ξ_n(x) d/dx_n be a germ at the origin of an analytic vector field. Suppose that ξ(0) != 0, and let γbe a trajectory of ξthrough the origin. Suppose that P|_γ/\equiv 0, and let μ(P|_γ) be the multiplicity of a zero of P|_γat the origin.

J. Kubo, M. Mondragon, G. Zoupanos

Gauge-Yukawa Unification (GYU) is obtained in GUTs by searching for renormalization group invariant relations among gauge and Yukawa couplings beyond the unification scale. Of particular interest are two supersymmetric GUTs, the finite and the minimal SU(5) models. Both models provided us,among others,with predictions of the top quark mass which so far have

Matteo Cacciari, Mario Greco

Fragmentation functions for D mesons, based on the convolution of a perturbative part, related to the heavy quark perturbative showering, and a non-perturbative model for its hadronization into the meson, are used to describe D^* production in e^+e^- and ep collisions. The non-perturbative part is determined by fitting the e^+e^- data taken by ARGUS and OPAL

Paul Hoyer

I discuss issues related to charmonium production, in view of physics possibilities at a 15 ... 30 GeV continuous beam electron facility. High energy photo- and hadroproduction of heavy quarkonia presents several challenges to QCD models concerning cross sections, polarization and nuclear target dependence. Theoretical approaches based on color evaporation a

Yuan-ben Dai, Chao-shang Huang, Ming-qiu Huang

The $O(1/m_Q)$ corrections to masses of excited heavy mesons are studied with sum rules in the heavy quark effective theory. Numerical results for the matrix elements of the heavy quark kinetic energy operator K and chromomagnetic interaction operator S are obtained for the lowest excited doublets $(0^+, 1^+)$ and $(1^+, 2^+)$.

V. V. Anisovich, D. V. Bugg, D. I. Melikhov, V. A. Nikonov

The background due to the direct diffractive dissociation of the photon into the $π^+π^-$-pair to the &#34;elastic&#34; diffractive $ρ^0$-meson production in electron-proton collisions is calculated. The amplitude for the background process $γp \to π^+ π^- p$ is proportional to the $π$-meson - proton cross section. Therefore, describing the HERA data, we can

Erwin Mirkes, Res Urech

Isospin violating signals in the tau -> 3 pi nu_tau decay mode are discussed. For the tau -> pi^- pi^- pi^+ nu_tau decay mode, isospin violation arises from the vector current contribution in the tau -> omega pi nu_tau decay with the subsequent isospin violating omega decay into pi^+ pi^-. We demonstrate that such effects may be observed in presently availab

H. P. de Oliveira, I. Damiao Soares, T. J. Stuchi

We study the dynamics of anisotropic Bianchi type-IX models with matter and cosmological constant. The models can be thought as describing the role of anisotropy in the early stages of inflation. The concurrence of the cosmological constant and anisotropy are sufficient to produce a chaotic dynamics in the gravitational degrees of freedom, connected to the p

Matt Visser

In this brief report I introduce a yet another class of geometries for which semi-classical chronology protection theorems are of dubious physical reliability. I consider a ``Roman ring&#39;&#39; of traversable wormholes, wherein a number of wormholes are arranged in a ring in such a manner that no subset of wormholes is near to chronology violation, though

K. Oerding, S. J. Cornell, A. J. Bray

The persistence exponent θfor the global order parameter, M(t), of a system quenched from the disordered phase to its critical point describes the probability, p(t) \sim t^{-θ}, that M(t) does not change sign in the time interval t following the quench. We calculate θto O(ε^2) for model A of critical dynamics (and to order εfor model C) and show that at this

Ute Ebert, Artur Baumgärtner, Lothar Schäfer

To establish a standard for the distinction of reptation from other modes of polymer diffusion, we analytically and numerically study the displacement of the central bead of a chain diffusing through an ordered obstacle array for times $t < O(N^2)$. Our theory and simulations agree quantitatively and show that the second moment approaches the $t^{1/4}$ often

Tetsuro Nikuni, A. E. Jacobs

In low magnetic field, the stacked, triangular antiferromagnet CsCuCl3 has a helical structure incommensurate (IC) in the chain direction. The IC wavenumber (from neutron-diffraction experiments) decreases with increasing field transverse to the chains, as predicted by classical theory, but then it has a plateau almost certainly caused by quantum fluctuation

Ken Yokoyama, Hidetoshi Fukuyama

The real part of the self-energy of interacting two-dimensional electrons has been calculated in the t-matrix approximation. It is shown that the forward scattering results in an anomalous term leading to the vanishing renormalization factor of the one-particle Green function, which is a non-perturbative effect of the interaction U. The present result is a m

Ioan Kosztin, Anthony J. Leggett

We show that, under certain conditions, the low temperature behavior of the magnetic penetration depth $λ(T)$ of a pure d-wave superconductor is determined by nonlocal electrodynamics and, contrary to the general belief, the deviation $Δλ(T) = λ(T)-λ(0)$ is proportional to T^2 and not T. We predict that the $Δλ(T)\propto T^2$ dependence, due to nonlocality,

David Vanderbilt, W. Zhong

We extend our previous first-principles theory for perovskite ferroelectric phase transitions to treat also antiferrodistortive phase transitions. Our approach involves construction of a model Hamiltonian from a Taylor expansion, first-principles calculations to determine expansion parameters, and Monte Carlo simulations to study the resulting system. We app

J. Padilla, David Vanderbilt

We have carried out first-principles total-energy calculations of (001) surfaces of the tetragonal and cubic phases of BaTiO3. Both BaO-terminated (type I) and TiO2-terminated (type II) surfaces are considered, and the atomic configurations have been fully relaxed. We found no deep-gap surface states for any of the surfaces, in agreement with previous theore

Jürgen König, Herbert Schoeller, Gerd Schön

We study electron transport through a small metallic island in the perturbative regime. Using a recently developed diagrammatic technique, we calculate the occupation of the island as well as the conductance through the transistor in forth order in the tunneling matrix elements, a process referred to as cotunneling. Our formulation does not require the intro

A. Furusaki

The orthogonality catastrophe in a Tomonaga-Luttinger liquid with an impurity is reexamined for the case when the interaction parameter or the dimensionless conductance is g=1/2. By transforming bosons back to fermions, the Hamiltonian is reduced to a quadratic form, which allows for explicit calculation of the overlap integral and the local density of state

P. Calvani, P. Dore, S. Lupi, A. Paolone

By comparing the optical conductivities of La_{1.67}Sr_{0.33}NiO_{4} (LSNO), Sr_{1.5}La_{0.5}MnO_4 (SLMO), Nd_2CuO_{4-y} (NCO), and Nd_{1.96}Ce_{0.04}CuO_{4} (NCCO), we have identified a peculiar behavior of polarons in this cuprate family. While in LSNO and SLMO small polarons localize into ordered structures below a transition temperature, in those cuprate

Madan Rao, Surajit Sengupta, R. Shankar

The Quantum Hall ground state away from $ν= 1$ can be described by a collection of interacting skyrmions. We show within the context of a nonlinear sigma model, that the classical ground state away from $ν= 1$ is a skyrmion crystal with a generalized Néel order. We show that as a function of filling $ν$, the skyrmion crystal undergoes a triangle to square to

Deepak Dhar

We consider a simple analytically tractable model of metastability and ageing. In this model, a particle can jump left or right by two steps to an unoccupied site, but only if the the site in between is occupied. We show that the model is strongly nonergodic, and the number of metastable states increases as exponential of the size of the system. Within a sec

James P. Crutchfield, David P. Feldman

We present exact results for two complementary measures of spatial structure generated by 1D spin systems with finite-range interactions. The first, excess entropy, measures the apparent spatial memory stored in configurations. The second, statistical complexity, measures the amount of memory needed to optimally predict the chain of spin values. These statis

B. C. den Hertog, M. P. Das

We suggest that when zinc is substituted for copper in the copper oxide planes of high $T_{c}$ superconductors, it does not necessarily have a valency of 2+. Rather, the valency of a zinc impurity should be determined by its surrounding medium. In order to study this hypothesis, we examine the effect of static impurities inducing diagonal disorder within a o

Markos Georganopoulos, Alan P. Marscher

A new continuous classification system for BL Lacertae (BL Lac) objects is proposed. The peak frequency of the synchrotron component in the $νL_ν$ spectrum is used as a classifying parameter. The application of the accelerating inner jet model to complete BL Lac samples suggests that the range of the observed properties may be explained by adopting a descrip

S. E. Church, K. M. Ganga, P. A. R. Ade, W. L. Holzapfel

We present limits to anisotropies in the cosmic microwave background radiation (CMB) at angular scales of a few arcminutes. The observations were made at a frequency of 142 GHz using a 6-element bolometer array (the Sunyaev-Zel&#39;dovich Infrared Experiment) at the Caltech Submillimeter Observatory. Two patches of sky, each approximately 36&#39;x4&#39; and

Roman Scoccimarro

I discuss new results concerning the evolution of the bispectrum due to gravitational instability from gaussian initial conditions using one-loop perturbation theory (PT). Particular attention is paid to the transition from weakly non-linear scales to the non-linear regime at small scales. Comparison with numerical simulations is made to assess the regime of

Przemyslaw Wozniak, Bohdan Paczynski

The current modelling of single microlensing light curves neglects the possibility that only a fraction of the light is due to the lensed star, the remaining being due to a close, unresolved blend, which may be related or unrelated to the lens. Unfortunately, the effects of blending are significant as all microlensing experiments choose very crowded fields a

F. Halzen, E. Zas

There are tantalizing hints that jets, powered by supermassive black holes at the center of active galaxies, are true cosmic proton accelerators. They produce photons of TeV energy, possible higher, and may be the enigmatic source of the highest energy cosmic rays. Photoproduction of neutral pions by accelerated protons on UV light is the source of the highe

K. Hurley, D. Hartmann, C. Kouveliotou, G. Fishman

A recent study has presented marginal statistical evidence that gamma-ray burst sources are correlated with Abell clusters, based on analyses of bursts in the BATSE 3B catalog. Using precise localization information from the 3rd Interplanetary Network, we have reanalyzed this possible correlation. We find that most of the Abell clusters which are in the rela

Michael Loewenstein, Richard Mushotzky

We address a number of misunderstandings and misstatements contained in the paper ``Roles of SNIa and SNII in ICM Enrichment&#39;&#39; by Y. Ishimaru and N. Arimoto with regard to the papers by Mushotzky et al. (1996, ApJ, 466, 686) and Loewenstein and Mushotzky (1996, ApJ, 466, 695). In particular, we emphasize that comparison between observations and model

Christoph Schaab, Bernd Hermann, Fridolin Weber, Manfred K. Weigel

The general statement that hypothetical strange (quark matter) stars cool more rapidly than neutron stars is investigated in greater detail. It is found that the direct Urca process could be forbidden not only in neutron stars but also in strange stars. In this case, strange stars are slowly cooling, and their surface temperatures are more or less indistingu

D. W. Sciama

In this paper we use a number of observations to construct an integrated picture of the ionisation in the interiors of quiescent warm opaque interstellar clouds and in the intercloud medium (ICM) outside dense HII regions and hot dilute bubbles. Our main conclusion is that within $\sim$ 1kpc of the sun the ionisation rate of hydrogen per unit volume in both

Ravi P. Pilla, Jacob Shaham

A new algorithm for implementing the adaptive Monte Carlo method is given. It is used to solve the relativistic Boltzmann equations that describe the time evolution of a nonequilibrium electron-positron pair plasma containing high-energy photons and pairs. The collision kernels for the photons as well as pairs are constructed for Compton scattering, pair ann

K. Ganga, Bharat Ratra, S. E. Church, Naoshi Sugiyama

We use arcminute-scale data from the Sunyaev-Zel&#39;dovich Infrared Experiment to set limits on anisotropies in the cosmic microwave background radiation in open and spatially-flat-Lambda cold dark matter cosmogonies. There are no 2-sigma detections for the models tested. The upper limits obtained are consistent with the amplitude of anisotropy detected by

W. D. Langer, T. Velusamy, T. B. H. Kuiper, R. Peng

The cumulene carbenes are important components of hydrocarbon chemistry in low mass star forming cores. Here we report the first astronomical detection of the long chain cumulene carbene H_2C_6 in the interstellar cloud TMC1, from observations of two of its rotational transitions: $J_{K,K&#39;} = 7_{1,7} \rightarrow 6_{1,6}$ at 18.8 GHz and $8_{1,8} \rightar

Robert C. Duncan, Hui Li

We consider a model for gamma-ray bursts (GRBs) from high-velocity neutron stars in the galactic halo. In this model, bursters are born in the galactic disk with large recoil velocities V_r, and GRBs are beamed to within emission cones of half-angle ϕcentered on V_r. We describe scenarios for magnetically -channeled GRBs that have such beaming characteristic

C. M. Gutierrez

Even the most sensitive cosmic microwave background anisotropy experiments have signal to noise ratios <=5, so that an accurate determination of the properties of the cosmological signal requires a careful assessment of the experimental noise. Most of the experiments combine simultaneous multi-channel observations in which the presence of correlated noise is

Yu. I. Manin, S. A. Merkulov

We introduce and study a superversion of Dubrovin&#39;s notion of semisimple Frobenius manifolds. We establish a correspondence between semisimple Frobenius (super)manifolds and special solutions to the (supersymmetric) Schlesinger equations. Finally, we calculate the Schlesinger initial conditions for solutions describing quantum cohomology of projective sp

Finn Larsen

The statistical mechanics of black holes arbitrarily far from extremality is modeled by a gas of weakly interacting strings. As an effective low energy description of black holes the model provides a number of highly non-trivial consistency checks and predictions. Speculations on a fundamental origin of the model suggest surprising simplifications in non-per

Y. M. Vilk, A. -M. S. Tremblay

A new approach to the single-band Hubbard model is described in the general context of many-body theories. It is based on enforcing conservation laws, the Pauli principle and a number of crucial sum-rules. More specifically, spin and charge susceptibilities are expressed, in a conserving approximation, as a function of two constant irreducible vertices whose

V. V. Fock

We describe in elementary geometrical terms Teichm\&#34; uller spaces of decorated and holed surfaces. We construct explicit global coordinates on them as well as on the spaces of measured laminations with compact and closed support respectively. We show explicitly that the latter spaces are asymptotically isomorphic to the former. We discuss briefly quantis

F. E. Low

The existence of run-away solutions in classical and non-relativistic quantum electrodynamics is reviewed. It is shown that the less singular high energy behavior of relativistic spin 1/2 quantum electrodynamics precludes an analogous behavior in that theory. However, a Landau-like anomalous pole in the photon propagation function or in the electron-massive

Miguel Navarro

New features of the generalized symmetries of generic two-dimensional dilaton models of gravity are presented and invariant gravity-matter couplings are introduced. We show that there is a continuum set of Noether symmetries, which contains half a de Witt algebra. Two of these symmetries are area-preserving transformations. We show that gravity-matter coupli

Jun Zang, Sudip Chakravarty, A. R. Bishop

The effects of interchain coupling on solitons and soliton lattice structures in CuGeO3 are explored. It is shown that interchain coupling substantially increases the soliton width and changes the soliton lattice structures in the incommensurate phase. It is proposed that the experimentally observed large soliton width in CuGeO3 is mainly due to interchain c

Xin Xue, Haiqing Wei

Superconducting rings with exactly $Φ_0/2$ magnetic flux threading are analogous of Ising spins having two degenerate states which can be used to store binary information. When brought close these rings interact by means of magnetic coupling. If the interactions are properly tailored, a system of such superconducting rings can accomplish static quantum logic

W. H. Tang, J. Smit

Using the (effective) classical approximation, we compute numerically time-dependent correlation functions in the SU(2)-Higgs model around the electroweak phase transition, for $m_H \approx m_W$. The parameters of the classical model have been determined previously by the dimensional reduction relations for time-independent correlators. The $H$ and $W$ corre

Haiqing Wei, Xin Xue

A quantum machine consisting of interacting linear clusters of atoms is proposed for the 3SAT problem. Each cluster with two relevant states of collective motion can be used to register a Boolean variable. Given any 3SAT Boolean formula the interactions among the clusters can be so tailored that the ground state(s) (possibly degenerate) of the whole system e

Tota Nakamura, Satoshi Takada, Kiyomi Okamoto, Naoki Kurosawa

We have obtained an analytic expression for the $k$ dependence of excitation energy gap for an arbitrary double $S=1/2$ spin-chain by using the nonlocal unitary transformation and the variational method. It is checked to explain the gap behavior of various systems, which include the Haldane system and the dimer system in both extreme limits, and also the lad

M. Vergassola, A. Mazzino

A one-dimensional white-in-time passive scalar model is introduced. Strong and persistent structures are shown to be present. A perturbative expansion for the scaling exponents is performed around a Gaussian limit of the model. The resulting predictions are compared with numerical simulations.

Alan L. Carey, Diarmuid Crowley, Michael K. Murray

A systematic consideration of the problem of the reduction and extension of the structure group of a principal bundle is made and a variety of techniques in each case are explored and related to one another. We apply these to the study of the Dixmier-Douady class in various contexts including string structures, U-res bundles and other examples motivated by c

Angelica de Oliveira-Costa, A. Kogut, Mark J. Devlin, C. Barth Netterfield

We cross-correlate the Saskatoon Ka and Q-Band Cosmic Microwave Background (CMB) data with different maps to quantify possible foreground contamination. We detect a marginal correlation (2 sigma) with the Diffuse Infrared Background Experiment (DIRBE) 240, 140 and 100 microm maps, but we find no significant correlation with point sources, with the Haslam 408

V. L. Vereschagin

The connection between modulated Riemann surface of genus one and solution to Volterra lattice that tends to constants at infinity is studied. The main term of asymptotics for large time of solution to the mentioned Cauchy problem is written out.

A. Cabo, J. L. Lucio, H. Mercado

We re-consider the quantum mechanics of scale invariant potentials in two dimensions. The breaking of scale invariance by quantum effects is analyzed by the explicit evaluation of the phase shift and the self-adjoint extension method. We argue that the breaking of scale invariance reported in the literature for the $δ$(r) potential, is an example of explicit

Salvatore De Martino, Silvio De Siena, Fabrizio Illuminati

We introduce a general formalism, based on the stochastic formulation of quantum mechanics, to obtain localized quasi-classical wave packets as dynamically controlled systems, for arbitrary anharmonic potentials. The control is in general linear, and it amounts to introduce additional quadratic and linear time-dependent terms to the given potential. In this